Cellular network systems may be arranged in multi-layer cellular systems—also referred to as heterogeneous networks (HetNet). In this context, multi-layer refers to cases with a mixture of macro base stations and small power base stations (for instance pico and micro). Macro-layer and pico/micro layer may also be implemented in different radio access technologies (RAT), for example GSM macro layer and LTE micro layer.
In such networks, a user equipment (UE) may use a measurement configuration. A measurement configuration defines how the UE will experience its environment and acts as an input to mobility management in connected mode (connected to a base station for an active communication) and autonomously in idle mode (without active communication). Typically, the Physical Cell Identity (PCI) is used to identify a cell for the radio without a need for the UE to read the broadcasted system information. The PCI of a cell is not necessarily a unique network-wide cell identifier. However, the PCI is normally unique on a local scale to avoid collision and/or confusion with neighboring cells.
In such networks, when the UE is moving, there may be the case where mobility problems for fast moving users are associated with out-bound handovers from small power cell, e.g. handout from pico cell to another pico or macro layer. In the connected mode, the triggering of a measurement report is controlled by a parameter, called TimeToTrigger (TTT), which is the same regardless of the target cell type. In idle mode, triggering a measurement for cell ranking is controlled with two broadcasted parameters, t-Reselection and Qhyst. When the UE is camping in a cell, these parameters may be the same during the measurements, regardless of the target cell type while measuring. Due to generic parameter settings, mobility problems may arise when a handover or a cell reselection is not performed towards the most suitable cell type because the target cell type is not taken into account.
Common measurement configuration setting is not fast enough to reconfigure measurements according to target cell types and the signaling load would not be feasible in heterogeneous network with dense small cells deployments. Also the support for measurement objects is limited where E-UTRAN configures only a single measurement object for a given frequency, i.e., it is not possible to configure two or more measurement objects for the same frequency with different associated parameters. This means that measurement configuration support for different cell types without reconfigurations is not possible.
The measurement configuration may have some flexibility only for fast moving UEs, which can use Mobility State Estimation (MSE) and related mobility parameters scaling. MSE scales down mobility parameters based on the estimated UE velocity and may make fast moving UEs to enter and leave small cells faster. Unfortunately, having UEs connected to small cells at high velocity is quite opposite to what is desired as the target is to improve mobility robustness and one conclusion is to keep fast moving UEs out of small cells.
There may be a need for an improved system and method being adapted to provide flexible radio measurements.